The hepatitis B virus (HBV) is an enveloped, partially double-stranded DNA virus. HBV is an infectious disease that affects the liver. Initial symptoms of infection may include vomiting, jaundice, lethargy, dark urine, and abdominal pain. Chronic HBV infection can result in cirrhosis and liver cancer. Currently available therapies can inhibit replication of the virus and minimize liver damage; however, there are no currently available therapies that can clear an HBV infection.
HBV surface antigen (HBsAg) is a protein located in the HBV envelope. It allows HBV virion entry into host cells by binding to the hepatocyte sodium-taurocholate cotransporting polypeptide (NTCP) receptor. HBsAg may also function as a tolerogen, suppressing immune elimination of infected cells. Total HBsAg loss and seroconversion are rarely achieved in chronically infected patients. Inhibiting HBsAg secretion and/or production is thus believed to be a strategy for the treatment of HBV infection, including chronic HBV infection. (Wieland, S. F. & F. V. Chisari, J. Virol. (2005), 79, 9369-80; Woltman et al. PLoS One (2011), 6, e15324; Op den Brouw et al. Immunology (2009b), 126, 280-89).